Electronic device

ABSTRACT

An electronic device includes a top plate having a first surface and a second surface that is positioned at an elevation that is lower than an elevation of the first surface, the second surface extending from a first end part of the top plate to a second end part of the top plate, a bottom plate provided under the top plate, and a circuit board placed between the top plate and the bottom plate and mounted with an electronic component. The top plate has opposing first and second edges and opposing third and fourth edges that are perpendicular to the first and the second edges, the first end part being formed at the first edge and the second end part being formed at the second edge.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/903,584, filed Feb. 23, 2018, which application is based upon andclaims the benefit of priority from Japanese Patent Application No.2017-050896, filed Mar. 16, 2017, the entire contents of which areincorporated herein by reference.

FIELD

Embodiments described herein relate generally to an electronic device.

BACKGROUND

Some electronic devices utilize airflows for heat dissipation. In suchdevices, blocking the airflows may result in insufficient heatdissipation.

DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view showing a schematic structure of anelectronic device relating to a first embodiment as seen from a side ofa top plate, and FIG. 1B is a perspective view showing a schematicstructure of the electronic device relating to the first embodiment asseen from a side of a bottom plate.

FIG. 2 is an exploded perspective view of the electronic device shown inFIG. 1A.

FIG. 3 is an exploded perspective view of a board assembly shown in FIG.2.

FIG. 4 is a sectional view showing a schematic structure of theelectronic device relating to the first embodiment.

FIG. 5 is a sectional view for showing an airflow condition whenmultiple electronic devices in FIG. 1A are stacked in a rack.

FIG. 6 is a perspective view showing a schematic structure of anelectronic device relating to a second embodiment as seen from a side ofa top plate.

FIG. 7 is a perspective view showing a schematic structure of anelectronic device relating to a third embodiment as seen from a side ofa top plate.

FIG. 8 is a perspective view showing a schematic structure of anelectronic device relating to a fourth embodiment as seen from a side ofa top plate.

FIG. 9 is an exploded perspective view of the electronic device shown inFIG. 8.

FIG. 10 is a perspective view showing a schematic structure of anelectronic device relating to a fifth embodiment as seen from a side ofa bottom plate.

DETAILED DESCRIPTION

Embodiments provide an electronic device with improved heat dissipatingcharacteristics.

In general, according to one embodiment, an electronic device includes atop plate, a bottom plate, and a circuit board. The top plate has afirst surface and a second surface that is positioned at an elevationthat is lower than an elevation of the first surface, the second surfaceextending from a first end part of the top plate to a second end part ofthe top plate. The bottom plate is provided under the top plate. Thecircuit board is placed between the top plate and the bottom plate andis mounted with an electronic component. The top plate has opposingfirst and second edges and opposing third and fourth edges that areperpendicular to the first and the second edges, the first end partbeing formed at the first edge and the second end part being formed atthe second edge.

Hereinafter, electronic devices relating to embodiments of the presentdisclosure will be described in detail with reference to the attacheddrawings. It is noted that these exemplary embodiments are not intendedto limit the scope of the present disclosure.

First Embodiment

FIG. 1A is a perspective view showing a schematic structure of anelectronic device relating to a first embodiment as seen from a side ofa top plate, and FIG. 1B is a perspective view showing a schematicstructure of the electronic device relating to the first embodiment asseen from a side of a bottom plate. FIG. 2 is an exploded perspectiveview of the electronic device shown in FIG. 1A. FIG. 3 is an explodedperspective view of a board assembly shown in FIG. 2. FIG. 4 is asectional view showing a schematic structure of the electronic devicerelating to the first embodiment.

The following description exemplifies a solid state drive (SSD) as anelectronic device in each embodiment. Although an electronic devicehaving three circuit boards is described in each embodiment, theelectronic device may have an “N” (where N is a positive integer) numberof circuit boards.

FIGS. 1A and 1B show an electronic device E1 having a top plate 1 and abottom plate 2. The top plate 1 may have opposing first and second sidesand opposing third and fourth sides that are perpendicular to the firstand the second sides. Hereinafter, the first and the second sides of thetop plate 1 correspond to front and back ends of the top plate 1, andthe third and the fourth sides of the top plate 1 correspond to left andright ends of the top plate 1. As shown in FIG. 2, a board assembly 10is placed between the top plate 1 and the bottom plate 2. The boardassembly 10 is formed with through holes 10A. The board assembly 10includes circuit boards 11, 13, and 15, as shown in FIG. 3.

As shown in FIGS. 1A, 1B, and 2, side plates 3A and 3B are respectivelyprovided at the front and back ends of the top plate 1. Side plates 4Aare respectively provided at left and right ends of the bottom plate 2,and a side plate 4B is provided at a back end of the bottom plate 2. Thetop plate 1, the bottom plate 2, the side plates 3A, 3B, 4A, and 4B mayenclose the board assembly 10.

The top plate 1 also has protrusions 1C. The protrusions 1C may beprovided at an outer edge part of the top plate 1. Although theprotrusions 1C are formed at six points of the outer edge part of thetop plate 1 in FIGS. 1A and 2, the protrusions 1C may be formed at atleast two points of the outer edge part of the top plate 1. Each of theprotrusions 1C is formed with a through hole 1D. The through hole 1D ismade to pass through a screw 6. The top plate 1 also has a rib 1A andrecesses 1B. The rib 1A increases the rigidity of the top plate 1. Therib 1A may be formed so as to protrude from the top plate 1 toward thebottom plate 2. The recesses 1B serve as paths for dissipating heatgenerated from the board assembly 10.

Each of the protrusions 1C is formed with a first surface MA1. The topplate 1 is formed with a second surface MA2. The second surface MA2 ispositioned at an elevation that is lower than an elevation of the firstsurfaces MA1 as seen from the side of the top plate 1. The secondsurface MA2 may include surfaces of the rib 1A and the recesses 1B.

The electronic device E1 has a height H1 that is determined by avertical distance from a bottom surface of the bottom plate 2 to thefirst surface MA1 of the protrusion 1C. The height H1 of the electronicdevice E1 may conform to the Small Form Factor (SFF) standard.

Airflows AF1 and AF2 can pass through among the protrusions 1C over thesecond surface MA2 of the top plate 1. The airflows AF1 and AF2 can passthrough in directions different from each other. For example, theairflows AF1 mainly pass through in the left and right direction of thetop plate 1, and the airflow AF2 mainly passes through in the front andback direction of the top plate 1.

As shown in FIG. 2, the bottom plate 2 is formed with screw holes 2A and2C. The screw holes 2A each are made to receive a screw 16. The screwholes 2C each are made to receive the screw 6. The screw 16 is insertedthrough the through hole 10A into the screw hole 2A to fix the boardassembly 10 to the bottom plate 2. The screw 6 is inserted through thethrough hole 1D into the screw hole 2C to fix the top plate 1 to thebottom plate 2.

Heat dissipating sheets 7A may be interposed between the top plate 1 andthe surface of the board assembly 10. Heat dissipating sheets 7B may beinterposed between the bottom plate 2 and a back surface of the boardassembly 10. In a condition in which the top plate 1 and the boardassembly 10 are fixed to the bottom plate 2 with the screws 6, the heatdissipating sheets 7A contact the top plate 1 and the surface of theboard assembly 10, and the heat dissipating sheets 7B contact the bottomplate 2 and the back surface of the board assembly 10. Each of the heatdissipating sheets 7A and 7B is preferably made of a heat-conductiveelastic material, and for example, an acrylic resin may be used.

As shown in FIGS. 3 and 4, NAND packages 17 are mounted on each of thecircuit boards 11, 13, and 15. The NAND packages 17 seal semiconductorchips, which are NAND flash memories (hereinafter referred to as “NANDmemories”). The NAND packages 17 may be mounted on both sides of each ofthe respective circuit boards 11, 13, and 15.

A connector 20B is mounted on a back surface of the circuit board 11. Aconnector 20A is mounted on a surface of the circuit board 13. Theconnector 20A is formed with pin holes P1. A connector 21B is mounted ona back surface of the circuit board 13. The circuit board 13 may beformed with a cutout 13B at a position corresponding to the positions ofcapacitors 19. A connector 21A, dynamic random access memory (DRAM)packages 18, and the capacitors 19 are mounted on a surface of thecircuit board 15. The capacitors 19 supply electric power to enablemovement of data stored in a dynamic random access memory (DRAM) to theNAND memory in case an external power source to the electronic device E1is cut off. The connector 21A is formed with pin holes P2. The DRAMpackages 18 seal semiconductor chips, which are DRAMs.

A controller package 22 is mounted on a back surface of the circuitboard 15. A connector T1 is mounted on an end of the circuit board 15.The controller package 22 seals a semiconductor chip, which is acontroller. The controller operates as an interface for exchanging readdata and write data between a host and the NAND memory. For example, thecontroller buffers read data and write data and performs errorcorrection code (ECC) processing, wear leveling processing, randomizingprocessing, and other processing. The wear leveling processing isconducted to avoid concentration of writing of data to a specific blockin the NAND memory. The randomizing processing is conducted to make datathat are written in the same block in the NAND memory to not haveperiodicity, thereby preventing inter-cell interference.

Each of the NAND packages 17, the DRAM packages 18, and the controllerpackage 22 may be a quad flat package (QFP), a ball grid array (BGA)package, a chip on board (COB) package, or a chip size package (CSP).The types of the NAND packages 17, the DRAM packages 18, and thecontroller package 22 may differ from each other. For example, the NANDpackages 17 and the DRAM packages 18 may be QFPs, and the controllerpackage 22 may be a COB package.

The board assembly 10 includes frame members 12 and 14. The frame member12 is formed with a reinforcing part 12B. The frame member 14 is formedwith a reinforcing part 14B.

The circuit boards 11, 13, and 15 and the frame members 12 and 14 arerespectively formed with through holes 11A, 13A, 15A, 12A, and 14A. Thethrough holes 11A, 13A, 15A, 12A, and 14A constitute the through holes10A of the board assembly 10. The through holes 11A, 13A, 15A, 12A, and14A each are made to pass through the screw 16. The through holes 11A,13A, 15A, 12A, and 14A may be provided at four corners of the respectivecircuit boards 11, 13, 15 and the frame members 12 and 14.

The frame member 12 is interposed between the circuit boards 11 and 13.The frame member 14 is interposed between the circuit boards 13 and 15.Pins of the connector 20B are inserted into the pin holes P1 of theconnector 20A, and pins of the connector 21B are inserted into the pinholes P2 of the connector 21A, whereby the board assembly 10 isassembled. The frame member 12 maintains a constant space between thecircuit boards 11 and 13. The frame member 14 maintains a constant spacebetween the circuit boards 13 and 15.

As shown in FIG. 4, heat dissipating sheets 7C may be placed between thecircuit boards 13 and 15. The heat dissipating sheets 7C may be placedat positions corresponding to the position of the controller package 22.The heat dissipating sheets 7B may be placed at positions correspondingto the position of the controller package 22 and the positions of theNAND packages 17 on the back surface of the circuit board 15. Moreover,the heat dissipating sheets 7B may also be placed on exothermiccomponents on the back surface of the circuit board 15. The heatdissipating sheets 7A may be placed at positions corresponding to thepositions of the recesses 1B and the positions of the NAND packages 17on the surface of the circuit board 11.

Arranging the heat dissipating sheets 7B and 7C at the positionscorresponding to the controller package 22 enables heat that isgenerated by the controller package 22 to be dissipated efficiently in avertical direction of the controller package 22.

Arranging the heat dissipating sheets 7A at the positions correspondingto the recesses 1B enables heat that is generated from the boardassembly 10 to be dissipated efficiently to the top plate 1. The heatthat is transmitted from the board assembly 10 to the top plate 1 isdissipated to the outside of the electronic device E1 by the airflowsAF1 and AF2.

The second surface MA2 of the top plate 1 is positioned lower than thefirst surfaces MA1. This structure allows the airflows AF1 and AF2 topass through over the second surface MA2 of the top plate 1 withoutchanging the height H1 of the electronic device E1. Thus, the heatdissipating characteristic of the electronic device E1 conforming to theSFF standard is improved, and therefore, the reliability of theelectronic device E1 is improved as well as equipment for assembling theelectronic device E1 and a package of the electronic device E1 are madecommon with other devices that conform to the SFF standard.

FIG. 5 is a sectional view for showing an airflow condition whenmultiple electronic devices in FIG. 1A are stacked in a rack.

FIG. 5 shows a rack 30 that is provided with ventilating holes K1 to K6,connectors T1′ to T6′, and fans F1 to F4. The rack 30 contains stackedelectronic devices E1 to E6. The electronic devices E1 to E6 may havethe same structure as the electronic device shown in FIG. 1A. In thiscondition, for example, a first surface MA1 of a lower stage electronicdevice E2 contacts a bottom surface of an upper stage electronic deviceE1 with a space between a second surface MA2 of the lower stageelectronic device E2 and the bottom surface of the upper stageelectronic device E1. This space is used as a ventilating path insidethe rack 30. The electronic devices E1 to E6 respectively haveconnectors T1 to T6, which are connectable to the correspondingconnectors T1′ to T6′ of the rack 30.

While the electronic devices E1 to E6 are powered on, the fans F1 to F4are operated. Then, airflows AF2 are generated inside the rack 30. Theairflows AF2 pass through between each of the electronic devices E1 toE6 and flow out from the respective ventilating holes K1 to K6.

At this time, the airflows AF2 cool the electronic devices E1 to E6.Ventilation resistance against the airflows AF2 flowing inside the rack30 is reduced, whereby the temperature inside the rack 30 is efficientlydecreased. The height H1 of each of the electronic devices E1 to E6 mayconform to the SFF standard. Thus, the electronic devices E1 to E6 arecontained in the rack 30 without changing the size of the rack 30 thatis suitable for the SFF standard.

Second Embodiment

FIG. 6 is a perspective view showing a schematic structure of anelectronic device relating to a second embodiment as seen from a side ofa top plate.

FIG. 6 shows an electronic device E7 that is provided with a top plate31, a bottom plate 32, and a connector T7. Side plates 33A arerespectively provided at front and back ends of the top plate 31. Sideplates 34A are respectively provided at left and right ends of thebottom plate 32. The configuration between the top plate 31 and thebottom plate 32 may be the same as that shown in FIGS. 2 to 4.

The top plate 31 is formed with recesses 31C. The recesses 31C may beprovided at an outer edge part of the top plate 31. Each of the recesses31C is formed with a through hole 31D. A screw 36 is inserted throughthe through hole 31D into a screw hole of the bottom plate 32 to fix thetop plate 31 to the bottom plate 32.

The top plate 31 is also formed with steps 31E. The steps 31E arerespectively provided at both sides of the top plate 31 to extend from afront end part to a back end part of the top plate 31. Each of the steps31E is formed with a first surface MB1 that extends from the front endpart to the back end part of the top plate 31. A second surface MB2 isbe formed at a further interior side than the steps 31E to extend fromthe front end part to the back end part of the top plate 31. The secondsurface MB2 is positioned at an elevation that is lower than anelevation of the first surfaces MB1 as seen from the side of the topplate 31. Airflows AF3 can pass through over the second surface MB2 fromthe front end part to the back end part of the top plate 31.

The electronic device E7 has a height H1 that is determined by avertical distance from a bottom surface of the bottom plate 32 to thefirst surface MB1 of the top plate 31. The height H1 of the electronicdevice E7 may conform to the SFF standard.

The second surface MB2 of the top plate 31 is positioned lower than thefirst surfaces MB1. This structure allows the airflows AF3 to passthrough over the second surface MB2 of the top plate 31 without changingthe height H1 of the electronic device E7. Thus, the heat dissipatingcharacteristic of the electronic device E7 conforming to the SFFstandard is improved.

Third Embodiment

FIG. 7 is a perspective view showing a schematic structure of anelectronic device relating to a third embodiment as seen from a side ofa top plate.

FIG. 7 shows an electronic device E8 that is provided with a top plate41, a bottom plate 42, and a connector T8. Side plates 43A arerespectively provided at front and back ends of the top plate 41. Sideplates 44A are respectively provided at left and right ends of thebottom plate 42. The configuration between the top plate 41 and thebottom plate 42 may be the same as that shown in FIGS. 2 to 4.

The top plate 41 is provided with recesses 41B and 41C. The recesses 41Bmay be provided at an interior side of the top plate 41. The recesses41B serve as paths for dissipating heat generated from the inside of theelectronic device E8. The recesses 41C may be provided at an outer edgepart of the top plate 41. Each of the recesses 41C is formed with athrough hole 41D. A screw 46 is inserted through the through hole 41Dinto a screw hole of the bottom plate 42 to fix the top plate 41 to thebottom plate 42.

The top plate 41 is also formed with steps 41E. The steps 41E arerespectively arranged at both sides of the top plate 41 to extend from aright end part to a left end part of the top plate 41. Each of the steps41E is formed with a first surface MC1 that extends from the right endpart to the left end part of the top plate 41. A second surface MC2 isformed at a further interior side than the steps 41E to extend from theright end part to the left end part of the top plate 41. The secondsurface MC2 is positioned at an elevation that is lower than anelevation of the first surfaces MC1 as seen from the side of the topplate 41. Airflows AF4 can pass through over the second surface MC2 fromthe right end part to the left end part of the top plate 41.

The electronic device E8 has a height H1 that is determined by avertical distance from a bottom surface of the bottom plate 42 to thefirst surface MC1 of the top plate 41. The height H1 of the electronicdevice E8 may conform to the SFF standard.

The second surface MC2 of the top plate 41 is positioned lower than thefirst surfaces MC1. This structure allows the airflows AF4 to passthrough over the second surface MC2 of the top plate 41 without changingthe height H1 of the electronic device E8. Thus, the heat dissipatingcharacteristic of the electronic device E8 conforming to the SFFstandard is improved.

Fourth Embodiment

FIG. 8 is a perspective view showing a schematic structure of anelectronic device relating to a fourth embodiment as seen from a side ofa top plate. FIG. 9 is an exploded perspective view of the electronicdevice shown in FIG. 8. This embodiment exemplifies an electronic devicemounted with two circuit boards.

FIG. 8 shows an electronic device E9 that is provided with a top plate51 and a bottom plate 52. As shown in FIG. 9, circuit boards 61 and 63are placed between the top plate 51 and the bottom plate 52.

A side plate 53A is provided at a front end of the top plate 51, andside plates 53B are respectively provided at left and right ends of thetop plate 51. The side plate 53A is provided with ventilating holes K9.Side plates 54A are respectively provided at left and right ends of thebottom plate 52, and a side plate 54B is provided at a front end of thebottom plate 52. The top plate 51, the bottom plate 52, the side plates53A, 53B, 54A, and 54B may enclose the circuit boards 61 and 63.

The top plate 51 is formed with ribs 51A and recesses 51B. The ribs 51Aincrease the rigidity of the top plate 51. The ribs 51A may be formed soas to protrude from the top plate 51 toward the bottom plate 52. Therecesses 51B serve as paths for dissipating heat generated from thecircuit boards 61 and 63.

The top plate 51 is also formed with steps 51E. Each of the steps 51E isprovided at an outer edge part of the top plate 51 to extend from afront end part to a back end part of the top plate 51. A first surfaceMD1 is formed at a further interior side than the steps 51E to extendfrom the front end part to the back end part of the top plate 51. Eachof the steps 51E is formed with a second surface MD2 that extends fromthe front end part to the back end part of the top plate 51. The secondsurfaces MD2 are positioned at an elevation that is lower than anelevation of the first surface MD1 as seen from the side of the topplate 51. Airflows AF5 can pass through over the second surfaces MD2from the front end part to the back end part of the top plate 51.

The top plate 51 is also formed with through holes 51C. The throughholes 51C may be provided in the second surfaces MD2. A screw 56A isinserted through the through hole 51C into a screw hole of the bottomplate 52 to fix the top plate 51 to the bottom plate 52.

The electronic device E9 has a height H2 that is determined by avertical distance from a bottom surface of the bottom plate 52 to thefirst surface MD1 of the top plate 51. The height H2 of the electronicdevice E9 may conform to the SFF standard. Arranging the through holes51C in the second surfaces MD2 prevents the heads of the screws 56A,which are inserted through the through holes 51C into the correspondingscrew holes of the bottom plate 52, from projecting higher than thefirst surface MD1. This structure provides an electronic device E8 witha height H2 conforming to the SFF standard.

The second surfaces MD2 of the top plate 51 are positioned lower thanthe first surface MD1. This structure allows the airflows AF5 to passthrough over the second surfaces MD2 of the top plate 51 withoutchanging the height H2 of the electronic device E9. Thus, the heatdissipating characteristic of the electronic device E9 conforming to theSFF standard is improved.

As shown in FIG. 9, the bottom plate 52 is formed with screw holes 52Ato 52C. The screw holes 52A to 52C may be provided at the four cornersof the bottom plate 52. A top surface of the screw hole 52A may beformed higher than a top surface of the screw hole 52B, and a topsurface of the screw hole 52B may be formed higher than a top surface ofthe screw hole 52C. The screw hole 52A is made to receive the screw 56A.The screw hole 52B is made to receive a screw 56B. The screw hole 52C ismade to receive a screw 56C.

The circuit boards 61 and 63 are mounted with NAND packages 67. The NANDpackages 67 may be mounted on both sides of the respective circuitboards 61 and 63.

Electronic components 62 and capacitors 69 are mounted on a surface ofthe circuit board 61. DRAM packages 68, electronic components 64, and aconnector 70 are mounted on a surface of the circuit board 63. Theelectronic components 62 and 64 may constitute a power source circuitand other circuits. A controller package is mounted on a back surface ofthe circuit board 63. A connector T9 is mounted on an end of the circuitboard 63. The connector 70 is formed with pin holes P3.

The circuit boards 61 and 63 are respectively formed with through holes61A and 63A. Each of the through holes 61A is made to receive a screw56B. Each of the through holes 63A is made to receive a screw 56C. Thethrough holes 61A and 63A may be provided at the four corners of therespective circuit boards 61 and 63.

Pins of a connector at a back surface of the circuit board 61 areinserted into the pin holes P3 of the connector 70 of the circuit board63. The screw 56C is inserted through the through hole 63A into thescrew hole 52C to fix the circuit board 63 to the bottom plate 52. Thescrew 56B is inserted through the through hole 61A into the screw hole52B to fix the circuit board 61 to the bottom plate 52. The screw 56A isinserted through the through hole 51C into the screw hole 52A to fix thetop plate 51 to the bottom plate 52.

The top surface of the screw hole 52A may be made higher than the topsurface of the screw hole 52B, and the top surface of the screw hole 52Bmay be made higher than the top surface of the screw hole 52C. Thisstructure enables maintaining a constant distance between the bottomplate 52 and the circuit board 63, between the circuit boards 61 and 63,and between the circuit board 61 and the top plate 51 without providingthe frame members 12 and 14 shown in FIG. 3. Heat dissipating sheets 57may be placed between the circuit board 63 and the bottom plate 52. Heatdissipating sheets may also be placed between the circuit board 61 andthe top plate 51.

As shown in FIG. 8, the second surfaces MD2 of the top plate 51 arepositioned lower than the first surface MD1. This structure allows theairflows AF5 to pass through over the second surfaces MD2 of the topplate 51 without changing the height H2 of the electronic device E9.Thus, the heat dissipating characteristic of the electronic device E9conforming to the SFF standard is improved, and therefore, thereliability of the electronic device E9 is improved as well as equipmentfor assembling the electronic device E9 and a package of the electronicdevice E9 are made common with other devices that conform to the SFFstandard.

Fifth Embodiment

FIG. 10 is a perspective view showing a schematic structure of anelectronic device relating to a fifth embodiment as seen from a side ofa bottom plate.

FIG. 10 shows an electronic device E10 that is provided with a bottomplate 2′ instead of the bottom plate 2 of the electronic device E1 shownin FIGS. 1A and 1B. The configuration except for the bottom plate 2′ ofthe electronic device E10 may be the same as that of the electronicdevice E1 shown in FIGS. 1A and 1B.

The bottom plate 2′ is formed with a step 2E. The step 2E extends from afront end part to a back end part of the bottom plate 2′. A firstsurface ME1 is provided at an outer side of the step 2E to extend from afront end part to a back end part of the bottom plate 2′. A secondsurface ME2 is provided at an inner side of the step 2E to extend fromthe front end part to the back end part of the bottom plate 2′. Thesecond surface ME2 is provided so as not to cross the connector T1. Thesecond surface ME2 is positioned at an elevation that is lower than anelevation of the first surface ME1 as seen from the side of the bottomplate 2′. An airflow AF6 can pass through over the second surface ME2from the front end part to the back end part of the bottom plate 2′.

The electronic device E10 has a height H1 that is determined by avertical distance from the first surface ME1 of the bottom plate 2′ tothe first surface MA1 of the top plate 1. The height H1 of theelectronic device E10 may conform to the SFF standard.

The second surface ME2 of the bottom plate 2′ is positioned lower thanthe first surface ME1. This structure allows the airflow AF6 to passthrough over the second surface ME2 of the bottom plate 2′ withoutchanging the height H1 of the electronic device E10. Thus, the heatdissipating characteristic of the electronic device E10 conforming tothe SFF standard is improved. Arranging the second surface ME2 at aposition not crossing the connector T1 eliminates the need for changingthe position of the connector T1, thereby providing the electronicdevice E10 conforming to the SFF standard.

Although the SSD is exemplified as the electronic device in each of theabove embodiments, any electronic device may be used. For example, theelectronic device may be a hard disk drive (HDD), a computer, or acommunication device.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. An electronic device comprising: a top platehaving opposing first and second edges, opposing third and fourth edgesthat are perpendicular to the first and the second edges, a firstportion with a first upper surface formed at an interior portion of thetop plate and along the first, second, and fourth edges, and a secondportion with a second upper surface at an elevation that is lower thanan elevation of the first upper surface, the second upper surface beingformed along an entire third edge of the top plate and to extend fromthe first edge of the top plate to the second edge of the top plate, thetop plate further including at least one screw hole formed on the secondportion; a bottom plate provided under the top plate; and a circuitboard placed between the top plate and the bottom plate and mounted withan electronic component, wherein the top plate further includes a rib onthe first portion and a plurality of recessed portions formed on therib, and wherein the rib is at an elevation that is lower than theelevation of the first upper surface, and each of the plurality ofrecessed portions is at an elevation that is lower than the elevation ofthe rib.
 2. The electronic device according to claim 1, wherein the topplate has a rectangular shape and the first and second edges are shortedges of the rectangular shape.
 3. The electronic device according toclaim 2, wherein the third and fourth edges are long edges of therectangular shape.
 4. The electronic device according to claim 1,wherein the first upper surface and the second upper surface form astep.
 5. The electronic device according to claim 1, further comprisinga plurality of heat dissipation sheets between the circuit board and oneor both of the top plate and the bottom plate.
 6. The electronic deviceaccording to claim 5, wherein the heat dissipation sheets contact thetop plate and the circuit board.
 7. The electronic device according toclaim 5, wherein the heat dissipation sheets contact the bottom plateand the circuit board.
 8. The electronic device according to claim 1,wherein a height from the bottom plate to the first upper surfaceconforms to Small Form Factor (SFF) standard.
 9. The electronic deviceaccording to claim 8, further comprising: a screw inserted through thescrew hole, wherein a head of the screw does not project higher than thefirst upper surface.